**3. Is there a difference between materials used in carotid angioplasty?**

As the CREST Trial showed, the risk of ICVA in CAS is a technical problem that remains unsolved [12]. A heavily debated topic in the literature is the design of the metallic alloy used to outline the empty spaces, which are called cells. Different types of frames for the metal skeleton can promote plaque stabilization, depending on the size of the free area between the metal brackets. Stents with a braided metallic mesh, which are dense throughout, can be more effective at covering the plaque and reducing the risk of embolism [30]. These closed-cell stents are characterized by small cells (areas enclosed by metal) joined together (Figure 1). Segmental rings connected to each other by points that are welded together and large areas that are not covered by metal are called open-cell stents [30]. Hybrid stents, which have a closed-cell design in their central part and an open-cell design in their proximal and distal parts, can also be found. These stents are rarely used in practice.

There are several examples of closed-cell stents, such as Wallstent® (Boston Scientific), Xact® (Abbott), and NexStent® (Endotex). The Carotid Wallstent® is considered the prototype for closed-cell design stents. Examples of stents with an open-cell design include Protégé® (Ev3), Precise® (Cordis), Acculink® (Abbott), and Exponent® (Medtronic). The Carotid Wallstent® model is manufactured with a stainless steel alloy and a closed-cell mesh, which may help to prevent embolic complications. Because of its design, the Carotid Wallstent® (Boston Scien‐ tific) undergoes a shortening by approximately 30% [31], and caution must be used when estimating its length. The Precise® (Cordis) stent is a nickel and titanium alloy (nitinol®) mounted on rings, which promotes an open-cell aspect and offers great flexibility. The Protégé® (Ev3) stent also uses nitinol and an open-cell design, and both conical and straight versions are available. These last two stents cannot be collected after they begin to release; therefore, they should only be opened when the implant site is certain. However, these stents do not undergo shortening.

A study by Tadros et al. used photomicroscopy to analyze debris found in the filters after CAS and showed that open-cell stents are associated with a larger mean particle size compared with closed-cell stents [32].

Doppler and MRI) have shown that an enormous load of emboli to the brain may not determine symptoms. This phenomenon is called an asymptomatic embolism associated with CAS.

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There are two types of cerebral protection systems: proximal and distal. The protection systems with filters are distal, and the protection devices with balloons can be proximal or distal. Proximal devices have the theoretical advantage of exerting protection during all phases of intervention, except during the positioning of the guide catheter or the long sheath. The proximal devices use temporary occlusion of the common carotid artery with a balloon, and a second balloon occludes the external carotid artery, resulting in the stagnation or reversal of the flow of the internal carotid artery (example: the PAES® Parodi antiembolism system). With this type of device, protection is initiated before the stenosis is crossed with the guide wire, which can reduce the risk of distal embolization. After the stent is implanted, the blood is aspirated from the carotid bifurcation to remove any fragments, and later, the proximal

In contrast, with the distal devices, it is necessary to cross the stenosis with the microguide and then to use the distal device on the lesion. Therefore, the distal systems consist of a device (filter or balloon) with an integrated guide wire. This set-up allows the CAS to be performed along the guide wire. With the distal protection, embolization can occur when the guide catheter or sheath is positioned and during the passage of the guide wire through the stenosis

Distal protection systems allow two different forms of approach. One form is the occlusion of the distal cervical internal carotid artery by a balloon (example: PercuSurge®). With this type of system, there is a complete interruption of the antegrade flow, which provides protection for the particles that do not reach the brain. After the CAS, manual aspiration is performed,

The other form of distal protection is through the use of a filter (examples: EPI®, Angio‐ guard®, Spider®). In this device, the filter (Figure 2) crosses the stenosis and is implant‐ ed in the distal cervical portion of the internal carotid artery. The stent and balloon are introduced over the guide to perform the CAS. There are different types of filters, but the aim of all of them is to retain particles, thereby preventing embolisms from reaching the brain and maintaining continuous blood flow. At the end of CAS, the filter is closed and removed from the patient with the embolic material inside [13]. In terms of design, the filters can be concentric (examples: Emboshield® and Angioguard® Cordis) or eccentric (examples: Filterwire EPI/EZ® Boston Scientific/Target and Spider®eV3). In concentric filters, the metallic guide occupies the center of the structure. In eccentric systems, the guide

Thus, the two main types of cerebral protection devices used in CAS are filters that allow distal flow during the CAS and systems for the temporary occlusion of the carotid artery (balloons) that promote the inversion or paralysis of flow to the brain. Some authors defend filtering devices, but others defend the balloons because they are believed to offer more complete protection of the brain. Furthermore, the use of these cerebral protection systems is not

protection device is removed [40-42].

before the distal device enters the action.

the balloon is deflated, and the system is removed [43,44].

is outside the center of the protection device [45,46].

supported in some patients.

**Figure 1.** Typical arrangement of the metal mesh of an open-cell stent (A) and a closed-cell stent (B). The area of a cell in each type of stent is highlighted in red

The results for angioplasty should be analyzed considering that there are ongoing major evolutions in methods and materials. The results of angioplasties after the introduction of stents and cerebral protection systems cannot be compared with the results of studies con‐ ducted before the development of these materials [13,32-37].

Although the initial purpose of carotid stenosis treatment is the prevention of cerebral infarction, both CEA and CAS carry risks of causing infarcts [13]. The materials and techniques have been modified to reduce the risk of embolic complications during CAS. Several authors [32-38] have shown the rare relative incidence of cerebral embolism and death after carotid angioplasty with or without cerebral protection.

Our experience with carotid angioplasty began in 1998 and 2000. At that time, cerebral protection systems were not available in Brazil. During this period, 72 CAS were performed, and the combination of neurological complications and death reached 5.5%. In the subsequent period (2001 to 2007), 1215 CASs were performed with filters for cerebral protection, and our occurrence of neurological complications and death fell to 1.8% [38].

Although some authors defend the use of CAS without cerebral protection, we emphasize that symptomatic embolism is rare and that the use of safety devices, such as cerebral protection systems, functions as a reserve parachute: Although they are rarely needed, no one wants to jump without one (recommendation class IIa, level of evidence: C, [39]).

Currently, several devices are capable of providing cerebral protection during carotid stenosis treatment, but the morbimortality results differ for each device. The forms of protection for each device are also different. Nonetheless, other authors using various methods (most notably Doppler and MRI) have shown that an enormous load of emboli to the brain may not determine symptoms. This phenomenon is called an asymptomatic embolism associated with CAS.

There are two types of cerebral protection systems: proximal and distal. The protection systems with filters are distal, and the protection devices with balloons can be proximal or distal. Proximal devices have the theoretical advantage of exerting protection during all phases of intervention, except during the positioning of the guide catheter or the long sheath. The proximal devices use temporary occlusion of the common carotid artery with a balloon, and a second balloon occludes the external carotid artery, resulting in the stagnation or reversal of the flow of the internal carotid artery (example: the PAES® Parodi antiembolism system). With this type of device, protection is initiated before the stenosis is crossed with the guide wire, which can reduce the risk of distal embolization. After the stent is implanted, the blood is aspirated from the carotid bifurcation to remove any fragments, and later, the proximal protection device is removed [40-42].

In contrast, with the distal devices, it is necessary to cross the stenosis with the microguide and then to use the distal device on the lesion. Therefore, the distal systems consist of a device (filter or balloon) with an integrated guide wire. This set-up allows the CAS to be performed along the guide wire. With the distal protection, embolization can occur when the guide catheter or sheath is positioned and during the passage of the guide wire through the stenosis before the distal device enters the action.

The results for angioplasty should be analyzed considering that there are ongoing major evolutions in methods and materials. The results of angioplasties after the introduction of stents and cerebral protection systems cannot be compared with the results of studies con‐

**Figure 1.** Typical arrangement of the metal mesh of an open-cell stent (A) and a closed-cell stent (B). The area of a cell

Although the initial purpose of carotid stenosis treatment is the prevention of cerebral infarction, both CEA and CAS carry risks of causing infarcts [13]. The materials and techniques have been modified to reduce the risk of embolic complications during CAS. Several authors [32-38] have shown the rare relative incidence of cerebral embolism and death after carotid

Our experience with carotid angioplasty began in 1998 and 2000. At that time, cerebral protection systems were not available in Brazil. During this period, 72 CAS were performed, and the combination of neurological complications and death reached 5.5%. In the subsequent period (2001 to 2007), 1215 CASs were performed with filters for cerebral protection, and our

Although some authors defend the use of CAS without cerebral protection, we emphasize that symptomatic embolism is rare and that the use of safety devices, such as cerebral protection systems, functions as a reserve parachute: Although they are rarely needed, no one wants to

Currently, several devices are capable of providing cerebral protection during carotid stenosis treatment, but the morbimortality results differ for each device. The forms of protection for each device are also different. Nonetheless, other authors using various methods (most notably

ducted before the development of these materials [13,32-37].

occurrence of neurological complications and death fell to 1.8% [38].

jump without one (recommendation class IIa, level of evidence: C, [39]).

angioplasty with or without cerebral protection.

in each type of stent is highlighted in red

152 Carotid Artery Disease - From Bench to Bedside and Beyond

Distal protection systems allow two different forms of approach. One form is the occlusion of the distal cervical internal carotid artery by a balloon (example: PercuSurge®). With this type of system, there is a complete interruption of the antegrade flow, which provides protection for the particles that do not reach the brain. After the CAS, manual aspiration is performed, the balloon is deflated, and the system is removed [43,44].

The other form of distal protection is through the use of a filter (examples: EPI®, Angio‐ guard®, Spider®). In this device, the filter (Figure 2) crosses the stenosis and is implant‐ ed in the distal cervical portion of the internal carotid artery. The stent and balloon are introduced over the guide to perform the CAS. There are different types of filters, but the aim of all of them is to retain particles, thereby preventing embolisms from reaching the brain and maintaining continuous blood flow. At the end of CAS, the filter is closed and removed from the patient with the embolic material inside [13]. In terms of design, the filters can be concentric (examples: Emboshield® and Angioguard® Cordis) or eccentric (examples: Filterwire EPI/EZ® Boston Scientific/Target and Spider®eV3). In concentric filters, the metallic guide occupies the center of the structure. In eccentric systems, the guide is outside the center of the protection device [45,46].

Thus, the two main types of cerebral protection devices used in CAS are filters that allow distal flow during the CAS and systems for the temporary occlusion of the carotid artery (balloons) that promote the inversion or paralysis of flow to the brain. Some authors defend filtering devices, but others defend the balloons because they are believed to offer more complete protection of the brain. Furthermore, the use of these cerebral protection systems is not supported in some patients.

An advantage of using filters is their ability to maintain constant flow to the brain during all stages of the angioplasty, unlike protection balloons, which promote the temporary halt of flow to the brain. Carotid filters are also easier to use than occlusive or reverse flow protection

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Despite the advantages of cerebral protection systems, Müller-Hülsbeck et al., in their 2005 study of ex vivo pig carotid arteries with four types of filters and one type of cerebral protection balloon, found that particles were passed with all of the protection systems tested [47]. Piñero et al. [48], using the transcranial Doppler technique, observed signs of embolism during several phases of CAS, including the initial unprotected phase. Similarly, Schimidt et al. [49] divided the carotid angioplasty into five phases from start to finish. This comparative study used one type of filter (EPI®) and one type of occlusive system with balloons (MO.MA®) and found

The transcranial Doppler tool can help identify signs of embolism during an unprotected phase (before using the filter) or during the passage of the filter, and it can identify embolisms when the stent or balloon is applied or the filter is removed [50,51]. The transcranial Doppler can provide information about the flow in the polygon vessels [52] and show changes in the cervical segment after angioplasty [53]. However, the Doppler assessment has the disadvantage of evaluating only one vessel, usually the middle cerebral artery or the distal cervical internal carotid artery on the carotid stenosis side, leaving a vast territory of the brain uncovered during the evaluation of embolic phenomena. No correlation can be observed between the quantity of microemboli identified during ultrasound and new embolism outbreaks found during MRI [54]. In contrast, MRI can evaluate the entire encephalon, which is particularly important because embolic events may occur during the CAS or during the angiography preceding CAS

According to several authors, the use of cerebral protection systems is an important factor in reducing the risk of cerebral infarction during CAS [9,13,34,55]. However, although most patients are asymptomatic after CAS, signs of embolism can be detected using the transcranial Doppler technique and MRI [56] because of different factors, such as the existence of pores in the protection systems that allow particles up to 100 microns pass, the manipulation of the artery before the filter is opened, the filter not adapting to the artery wall, and crucially, a lack

We consider MRI an excellent method for evaluating cerebral ischemia in its various presen‐ tations. An MRI study of various acute neurological presentations of an ischemic nature

in other areas of the brain supplied by the carotid undergoing CAS [46,48].

of proper training in handling the systems [46,48,49,54,57-63].

includes several forms of ischemia presentation on the images [64].

**5. Imaging evaluation of cerebral embolism**

**4. Cerebral embolism in the surgical treatment of carotid stenosis**

that particles were passed in all phases of both systems.

balloons.

**Figure 2.** Examples of cerebral protection devices: eccentric design (A) in the EPI® filter and concentric design (B) in the Emboshield® system

Although all devices have a common goal of preventing the entry of particles into distal circulation, the perfect protection system does not exist [42]. Among proximal protection systems with balloons, arterial occlusion is the weakest point because patients might not tolerate it. Moreover, the contrast of vessels during the CAS is difficult because of flow stagnation, which makes positioning the stent difficult. Moreover, this system is more laborious and complex to use than filters. Additionally, proximal protection systems are very high profile and tend to lead to hemorrhaging complications at the puncture site. The device's advantages include its ability to initiate cerebral protection at an early stage and to avoid embolization during the initial passage of the wire through the stenosis [13,42].

The distal embolic protection devices with a balloon have the disadvantage of preventing antegrade flow, which renders some patients intolerant of this type of device. The balloon may also cause vascular lesions (example: pseudoaneurysm), and the affixture of the balloon may be lost during the CAS. Moreover, images cannot be easily obtained while the balloon is in use and, technically, the balloon is not very maneuverable. An advantage of distal protection devices is their ease of use compared with proximal occlusion balloons [13].

Among the disadvantages of distal embolic protection devices with filters is that they may not capture all particles and their delivery and recovery systems may cause embolisms. Some filters may attach to the stent because of bad handling. The advantages of filters include the preservation of antegrade flow to the brain during all stages of the CAS and the ability to obtain graphic images easily. Some systems allow the operator to select which guide wire to use to cross the lesion, which allows the filter to remain in contact with the arterial wall and the guide wire to be moved during the CAS without mobilizing the filter [13].

An advantage of using filters is their ability to maintain constant flow to the brain during all stages of the angioplasty, unlike protection balloons, which promote the temporary halt of flow to the brain. Carotid filters are also easier to use than occlusive or reverse flow protection balloons.
